RadzenListBox does not show the current selection when not in multi-select mode. If you click on the item, it internally appears to be selected (i.e. events fire) but there is no UI feedback that the item is selected. If you use the keyboard to scroll items, you do see a selection, so this is more about behavior with mouse clicks, it seems.
I have worked around this by allowing multiple selections, handle Change, then change the selection to be the last value selected. Not ideal but it works to give feedback on the current selection.
Hi @codexguy,
Thank you for reporting this issue! We will address it with the next Radzen.Blazor release.